My elderly grandmother needs to know who her dad was

My elderly grandmother needs to know who her dad was

Yolanda Gonzalez was born to a woman named Herminia Chacon.DOB 2-17-03 in Las Vegas New Mexico. We don't know why she took this name as she claimed to never have married so should have remained Gonzales. Yolanda has a living sister named Delores whom she was raised to believe was her cousin. Originally Yolanda was told she was born in Silver City New Mexico DOB 1-11-26. However there is no record of her being born there. Before her mom (Herminia Chacon) died she told her she was actually born in El Paso. There is one living person with knowledge of who YOlandas father is. Herminia's sister Vera. She swears to honor her sister's wishes and take it to the grave. If anyone can help me untangle this mess to give my grandmother peace it would be a blessing.